Inhibition of Renal Sodium-Glucose Cotransport With Empagliflozin Lowers Fasting Plasma Glucose and Improves β-Cell Function in Subjects With Impaired Fasting Glucose

Pancreatic beta-cell mass and function and therapeutic implications of using antidiabetic medications in type 2 diabetes

Nowadays, the focus of diabetes treatment has switched from lowering the glucose level to preserving glycemic homeostasis and slowing the disease progression. The main pathophysiology of both type 1 diabetes and long-standing type 2 diabetes is pancreatic β-cell mass loss and dysfunction. According to recent research, human pancreatic β-cells possess the ability to proliferate in response to elevated insulin demands. It has been demonstrated that in insulin-resistant conditions in humans, such as obesity or pregnancy, the β-cell mass increases. This ability could be helpful in developing novel treatment approaches to restore a functional β-cell mass. Treatment strategies aimed at boosting β-cell function and mass may be a useful tool for managing diabetes mellitus and stopping its progression. This review outlines the processes of β-cell failure and detail the many β-cell abnormalities that manifest in people with diabetes mellitus. We also go over standard techniques for determining the mass and function of β-cells. Lastly, we provide the therapeutic implications of utilizing antidiabetic drugs in controlling the mass and function of pancreatic β-cells.

The impact of increased hepatic glucose production caused by empagliflozin on plasma glucose concentration in individuals with type 2 diabetes and nondiabetic individuals

AIM

To examine the impact of increased hepatic glucose production (HGP) on the decrease in plasma glucose concentration caused by empagliflozin in individuals living with diabetes and in nondiabetic individuals.

METHODS

A total of 36 individuals living with diabetes and 34 nondiabetic individuals were randomized to receive, in double-blind fashion, empagliflozin or matching placebo in a 2:1 treatment ratio. Following an overnight fast, HGP was measured with 3-3 H-glucose infusion before, at the start of, and 3 months after therapy with empagliflozin.

RESULTS

On Day 1 of empagliflozin administration, the increase in urinary glucose excretion (UGE) in individuals with normal glucose tolerance was smaller than in those with impaired glucose tolerance and those living with diabetes, and was accompanied by an increase in HGP in all three groups. The amount of glucose returned to the systemic circulation as a result of the increase in HGP was smaller than that excreted by the kidney during the first 3 h after empagliflozin administration, resulting in a decrease in fasting plasma glucose (FPG) concentration. After 3 h, the increase in HGP was in excess of UGE, leading to a small increase in plasma glucose concentration, which reached a new steady state. After 12 weeks, the amount of glucose returned to the circulation due to the empagliflozin-induced increase in HGP was comparable with that excreted by the kidney in all three groups.

CONCLUSION

The balance between UGE and increase in HGP immediately after sodium-glucose cotransporter-2 (SGLT2) inhibition determined the magnitude of decrease in FPG and the new steady state which was achieved. After 12 weeks, the increase in HGP caused by empagliflozin closely matched the amount of glucose excreted by the kidneys; thus, FPG level remained stable despite the continuous urinary excretion of glucose caused by SGLT2 inhibition.

Empagliflozin improves insulin sensitivity in patients with recent acute coronary syndrome and newly detected dysglycaemia : Experiences from the randomized, controlled SOCOGAMI trial

BACKGROUND

Empagliflozin reduces the risk of cardiovascular disease (CVD) in patients with type 2 diabetes (T2DM) and high cardiovascular risk via mechanisms which have not been fully explained. The mechanisms of such benefit have not been fully understood, and whether empagliflozin can be safely administered as first-line treatment in patients with CVD at the initial stages of glycaemic perturbations remains to be established. We investigated the effects of empagliflozin on insulin resistance, insulin sensitivity and β-cell function indexes in patients with a recent acute coronary event and newly detected dysglycaemia, i.e., impaired glucose tolerance (IGT) or T2DM.

METHODS

Forty-two patients (mean age 67.5 years, 19% females) with a recent myocardial infarction (n = 36) or unstable angina (n = 6) and newly detected dysglycaemia were randomized to either empagliflozin 25 mg daily (n = 20) or placebo (n = 22). Patients were investigated with stress-perfusion cardiac magnetic resonance imaging before randomization, 7 months after the start of study drug and 3 months following its cessation. Indexes of insulin resistance, sensitivity and β-cell function were calculated based on glucose and insulin values from 2-hour oral glucose tolerance tests (OGTT) and fasting C-peptide. The differences in glucose, insulin, C-peptide, mannose levels and indexes between the two groups were computed by repeated measures ANOVA including an interaction term between the treatment allocation and the time of visit.

RESULTS

After 7 months, empagliflozin significantly decreased glucose and insulin values during the OGTT, whereas C-peptide, mannose and HbA1c did not differ. Empagliflozin significantly improved insulin sensitivity indexes but did not impact insulin resistance and β-cell function. After cessation of the drug, all indexes returned to initial levels. Insulin sensitivity indexes were inversely correlated with left ventricular mass at baseline.

CONCLUSIONS

Empagliflozin improved insulin sensitivity indexes in patients with a recent coronary event and drug naïve dysglycaemia. These findings support the safe use of empagliflozin as first-line glucose-lowering treatment in patients at very high cardiovascular risk with newly diagnosed dysglycaemia.

TRIAL REGISTRATION NUMBER

EudraCT number 2015-004571-73.

New-onset diabetes with sodium-glucose cotransporter-2 inhibitors in prediabetes: An updated meta-analysis and possible mechanisms

BACKGROUND AND AIMS

A recent systematic review and meta-analysis studied the effect of sodium-glucose cotransporter-2 inhibitors (SGLT2i) on new-onset diabetes (NOD) in adults with prediabetes having chronic kidney disease and heart failure. In light of other large randomized controlled trials (RCTs) of SGLT2i published after this meta-analysis that also reported the NOD outcome in adults with prediabetes, it is of interest to update the NOD outcome with SGLT2i.

METHODS

A systemic search in the PubMed and Embase electronic database was made until March 31, 2023, using specific MeSH keywords following PRISMA protocol. Subsequently, we conducted a meta-analysis using the random effects model while applying the inverse variance-weighted averages of pooled logarithmic hazard ratio (HR). Heterogeneity was measured using Higgins I² and Cochrane Q statistics and publication bias was evaluated by applying funnel plots. A sensitivity exclusion analysis was additionally made.

RESULTS

This meta-analysis of five RCTs (N = 6752) found a significant reduction in NOD (HR 0.81; 95% CI, 0.69-0.94; P = 0.005) with SGLT2i in adults with prediabetes without any heterogeneity (I² = 0%).

CONCLUSIONS

SGLT2i has the potential to reduce NOD in adults with prediabetes. Since no effect on HbA1c reduction was seen in adults with prediabetes in all five RCTs included in this meta-analysis, it is conceivable that reduction in NOD is not related to the masking of blood glucose exerted by SGLT2i. However, only an adequately powered trial of SGLT2i in people with prediabetes with a sufficient wash-out period will confirm these findings.

Empagliflozin Ameliorates Progression From Prediabetes to Diabetes and Improves Hepatic Lipid Metabolism: A Systematic Review

Diabetes mellitus (DM) and hepatic steatosis are two of the most common metabolic syndromes that affect the health of people globally. Empagliflozin (EMPA) is a promising drug of choice for the diabetic population. Recent studies have shown its beneficial effects not only on diabetic patients but also on patients suffering from cardiac, hepatic, neurological, or pancreatic anomalies. In this paper, we systematically searched electronic databases to compile literature that focuses on EMPA’s effect on the prediabetic population, diabetic population, and hepatic lipid metabolism. We focus on the mechanism of EMPA, specifically by which it increases insulin sensitivity and fat browning and reduces fat accumulation. Overall, we hypothesized that by its effect on weight loss and reducing inflammatory markers and insulin resistance (IR), EMPA decreases the rate of prediabetes to diabetes conversion. We concluded that by improving hepatic and serum triglyceride, decreasing visceral fat, and its positive impact on hepatic steatosis, the drug improves hepatic lipid metabolism. Further research should be done on this matter.

SGLT-2 inhibitors and GLP-1 receptor agonists in metabolic dysfunction-associated fatty liver disease

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a chronic condition that affects nearly one billion people globally, characterized by triacylglycerol accumulation in the liver as a consequence of metabolic abnormalities (obesity and impaired glucose regulation). Low-grade inflammation, oxidative stress, mitochondrial dysfunction, and dysbiosis in gut microbiota are involved in the etiology of MAFLD, and both cardiovascular events and hepatic complications are the long-term consequences. In the absence of approved therapies for this condition, sodium-glucose cotransporter 2 inhibitors (SGLT-2 Is) and glucagon-like peptide 1 receptor agonists (GLP-1 RAs) have the specific advantage of lowering body weight and providing cardiovascular benefits. Here, we discuss potential roles for SGLT-2 Is and GLP-1 RAs in the prevention and treatment of intrahepatic triacylglycerol accumulation and associated inflammation and/or fibrosis.

Effects of Sodium-Glucose Co-Transporter-2 Inhibitors on Pancreatic β-Cell Mass and Function

Sodium-glucose co-transporter-2 inhibitors (SGLT2is) not only have antihyperglycemic effects and are associated with a low risk of hypoglycemia but also have protective effects in organs, including the heart and kidneys. The pathophysiology of diabetes involves chronic hyperglycemia, which causes excessive demands on pancreatic β-cells, ultimately leading to decreases in β-cell mass and function. Because SGLT2is ameliorate hyperglycemia without acting directly on β-cells, they are thought to prevent β-cell failure by reducing glucose overload in this cell type. Several studies have shown that treatment with an SGLT2i increases β-cell proliferation and/or reduces β-cell apoptosis, resulting in the preservation of β-cell mass in animal models of diabetes. In addition, many clinical trials have shown that that SGLT2is improve β-cell function in individuals with type 2 diabetes. In this review, the preclinical and clinical data regarding the effects of SGLT2is on pancreatic β-cell mass and function are summarized and the protective effect of SGLT2is in β-cells is discussed.

Pharmacokinetics and Bioequivalence of Two Empagliflozin, with Evaluation in Healthy Jordanian Subjects under Fasting and Fed Conditions

The current study is a randomized, open-label, two-period, two-sequence, two-way crossover pharmacokinetic study in healthy Jordanian subjects to evaluate the pharmacokinetics and bioequivalence profile of two cases of empagliflozin 10 mg under fasting and fed conditions. The plasma concentrations of empagliflozin were determined using an HPLC-MS/MS method. Tolerability and safety were assessed throughout the study. This study included 26 subjects, 26 in both fasting and fed groups.The pharmacokinetic parameters, which included the area under the concentration–time curve from time zero to infinity (AUC_0–inf) and the final quantifiable concentration (AUC_0–last), maximum serum concentration (C_max), and time to reach the maximum drug concentration (T_max) were found to be within an equivalence margin of 80.00–125.00%. The pharmacokinetic profiles show that the empagliflozin test and parent reference cases were bioequivalent in healthy subjects. The two treatments’ safety evaluations were also comparable.

Empagliflozin Improves Insulin Sensitivity of the Hypothalamus in Humans With Prediabetes: A Randomized, Double-Blind, Placebo-Controlled, Phase 2 Trial

OBJECTIVE

Insulin action in the human brain reduces food intake, improves whole-body insulin sensitivity, and modulates body fat mass and its distribution. Obesity and type 2 diabetes are often associated with brain insulin resistance, resulting in impaired brain-derived modulation of peripheral metabolism. So far, no pharmacological treatment for brain insulin resistance has been established. Since sodium-glucose cotransporter 2 (SGLT2) inhibitors lower glucose levels and modulate energy metabolism, we hypothesized that SGLT2 inhibition may be a pharmacological approach to reverse brain insulin resistance.

RESEARCH DESIGN AND METHODS

In this randomized, double-blind, placebo-controlled clinical trial, 40 patients (mean ± SD; age 60 ± 9 years; BMI 31.5 ± 3.8 kg/m2) with prediabetes were randomized to receive 25 mg empagliflozin every day or placebo. Before and after 8 weeks of treatment, brain insulin sensitivity was assessed by functional MRI combined with intranasal administration of insulin to the brain.

RESULTS

We identified a significant interaction between time and treatment in the hypothalamic response to insulin. Post hoc analyses revealed that only empagliflozin-treated patients experienced increased hypothalamic insulin responsiveness. Hypothalamic insulin action significantly mediated the empagliflozin-induced decrease in fasting glucose and liver fat.

CONCLUSIONS

Our results corroborate insulin resistance of the hypothalamus in humans with prediabetes. Treatment with empagliflozin for 8 weeks was able to restore hypothalamic insulin sensitivity, a favorable response that could contribute to the beneficial effects of SGLT2 inhibitors. Our findings position SGLT2 inhibition as the first pharmacological approach to reverse brain insulin resistance, with potential benefits for adiposity and whole-body metabolism.

GLP-1 RAs and SGLT-2 Inhibitors for Insulin Resistance in Nonalcoholic Fatty Liver Disease: Systematic Review and Network Meta-Analysis

OBJECTIVE

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and sodium-glucose cotransporter-2 (SGLT-2) inhibitors reduce glycaemia and weight and improve insulin resistance (IR) via different mechanisms. We aim to evaluate and compare the ability of GLP-1 RAs and SGLT-2 inhibitors to ameliorate the IR of nonalcoholic fatty liver disease (NAFLD) patients.

DATA SYNTHESIS

Three electronic databases (Medline, Embase, PubMed) were searched from inception until March 2021. We selected randomized controlled trials comparing GLP-1 RAs and SGLT-2 inhibitors with control in adult NAFLD patients with or without T2DM. Network meta-analyses were performed using fixed and random effect models, and the mean difference (MD) with corresponding 95% confidence intervals (CI) were determined. The within-study risk of bias was assessed with the Cochrane collaborative risk assessment tool RoB.

RESULTS

25 studies with 1595 patients were included in this network meta-analysis. Among them, there were 448 patients, in 6 studies, who were not comorbid with T2DM. Following a mean treatment duration of 28.86 weeks, compared with the control group, GLP-1 RAs decreased the HOMA-IR (MD [95%CI]; -1.573[-2.523 to -0.495]), visceral fat (-0.637[-0.992 to -0.284]), weight (-2.394[-4.625 to -0.164]), fasting blood sugar (-0.662[-1.377 to -0.021]) and triglyceride (- 0.610[-1.056 to -0.188]). On the basis of existing studies, SGLT-2 inhibitors showed no statistically significant improvement in the above indicators. Compared with SGLT-2 inhibitors, GLP-1 RAs decreased visceral fat (-0.560[-0.961 to -0.131]) and triglyceride (-0.607[-1.095 to -0.117]) significantly.

CONCLUSIONS

GLP-1 RAs effectively improve IR in NAFLD, whereas SGLT-2 inhibitors show no apparent effect.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO https://www.crd.york.ac.uk/PROSPERO/, CRD42021251704.

Empagliflozin therapy and insulin resistance-associated disorders: effects and promises beyond a diabetic state

Empagliflozin is a SGLT2 inhibitor that has shown remarkable cardiovascular and renal activities in patients with type 2 diabetes (T2D). Preclinical and clinical studies of empagliflozin in T2D population have demonstrated significant improvements in body weight, waist circumference, insulin sensitivity, and blood pressure – effects beyond its antihyperglycaemic control. Moreover, several studies suggested that this drug possesses significant anti-inflammatory and antioxidative stress properties. This paper explores extensively the main preclinical and clinical evidence of empagliflozin administration in insulin resistance-related disorders beyond a diabetic state. It also discusses its future perspectives, as a therapeutic approach, in this high cardiovascular-risk population.

Unexpected Pleiotropic Effects of SGLT2 Inhibitors: Pearls and Pitfalls of This Novel Antidiabetic Class

Sodium-glucose co-transporter 2 (SGLT2) inhibitors facilitate urine glucose excretion by reducing glucose reabsorption, leading to ameliorate glycemic control. While the main characteristics of type 2 diabetes mellitus are insufficient insulin secretion and insulin resistance, SGLT2 inhibitors have some favorable effects on pancreatic β-cell function and insulin sensitivity. SGLT2 inhibitors ameliorate fatty liver and reduce visceral fat mass. Furthermore, it has been noted that SGLT2 inhibitors have cardio-protective and renal protective effects in addition to their glucose-lowering effect. In addition, several kinds of SGLT2 inhibitors are used in patients with type 1 diabetes mellitus as an adjuvant therapy to insulin. Taken together, SGLT2 inhibitors have amazing multifaceted effects that are far beyond prediction like some emerging magical medicine. Thereby, SGLT2 inhibitors are very promising as relatively new anti-diabetic drugs and are being paid attention in various aspects. It is noted, however, that SGLT2 inhibitors have several side effects such as urinary tract infection or genital infection. In addition, we should bear in mind the possibility of diabetic ketoacidosis, especially when we use SGLT2 inhibitors in patients with poor insulin secretory capacity.

Impact of SGLT-2 Inhibition on Cardiometabolic Abnormalities in a Rat Model of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in reproductive-age women. PCOS is characterized by hyperandrogenism and ovulatory dysfunction. Women with PCOS have a high prevalence of obesity, insulin resistance (IR), increased blood pressure (BP), and activation of the renin angiotensin system (RAS). Effective evidence-based therapeutics to ameliorate the cardiometabolic complications in PCOS are lacking. The sodium-glucose cotransporter-2 (SGLT2) inhibitor Empagliflozin (EMPA) reduces BP and hyperglycemia in type 2 diabetes mellitus. We hypothesized that hyperandrogenemia upregulates renal SGLT2 expression and that EMPA ameliorates cardiometabolic complications in a hyperandrogenemic PCOS model. Four-week-old female Sprague Dawley rats were treated with dihydrotestosterone (DHT) for 90 days, and EMPA was co-administered for the last three weeks. DHT upregulated renal SGLT2, SGLT4, and GLUT2, but downregulated SGLT3 mRNA expression. EMPA decreased DHT-mediated increases in fat mass, plasma leptin, and BP, but failed to decrease plasma insulin, HbA1c, or albuminuria. EMPA decreased DHT-mediated increase in renal angiotensin converting enzyme (ACE), angiotensin converting enzyme 2 (ACE2), and angiotensin II type 1 receptor (AGT1R) mRNA and protein expression. In summary, SGLT2 inhibition proved beneficial in adiposity and BP reduction in a hyperandrogenemic PCOS model; however, additional therapies may be needed to improve IR and renal injury.

No effects of dapagliflozin, metformin or exercise on plasma glucagon concentrations in individuals with prediabetes: A post hoc analysis from the randomized controlled PRE-D trial

AIM

To assess the effects of dapagliflozin, metformin and exercise treatment on changes in plasma glucagon concentrations in individuals with overweight and HbA1c-defined prediabetes.

MATERIALS AND METHODS

One-hundred and twenty individuals with overweight (body mass index ≥ 25 kg/m² ) and prediabetes (HbA1c of 39-47 mmol/mol) were randomized to a 13-week intervention with dapagliflozin (10 mg once daily), metformin (850 mg twice daily), exercise (30 minutes of interval training 5 days per week) or control (habitual living). A 75-g oral glucose tolerance test (OGTT) (0, 30, 60 and 120 minutes) was administered at baseline, at 13 weeks (end of intervention) and at 26 weeks (end of follow-up). Linear mixed effects models with participant-specific random intercepts were used to investigate associations of the interventions with fasting plasma glucagon concentration, insulin/glucagon ratio and glucagon suppression during the OGTT.

RESULTS

At baseline, the median (Q1; Q3) age was 62 (54; 68) years, median fasting plasma glucagon concentration was 11 (7; 15) pmol/L, mean (SD) HbA1c was 40.9 (2.3) mmol/mol and 56% were women. Compared with the control group, fasting glucagon did not change in any of the groups from baseline to the end of the intervention (dapagliflozin group: -5% [95% CI: -29; 26]; exercise group: -8% [95% CI: -31; 24]; metformin group: -2% [95% CI: -27; 30]). Likewise, there were no differences in insulin/glucagon ratio and glucagon suppression during the OGTT between the groups.

CONCLUSIONS

In individuals with prediabetes, 13 weeks of treatment with dapagliflozin, metformin or exercise was not associated with changes in fasting or post-OGTT glucagon concentrations.

SGLT2 is not expressed in pancreatic α- and β-cells, and its inhibition does not directly affect glucagon and insulin secretion in rodents and humans

Objective

Sodium-glucose cotransporter 2 (SGLT2) inhibitors (SGLT2i), or gliflozins, are anti-diabetic drugs that lower glycemia by promoting glucosuria, but they also stimulate endogenous glucose and ketone body production. The likely causes of these metabolic responses are increased blood glucagon levels, and decreased blood insulin levels, but the mechanisms involved are hotly debated. This study verified whether or not SGLT2i affect glucagon and insulin secretion by a direct action on islet cells in three species, using multiple approaches.

Methods

We tested the in vivo effects of two selective SGLT2i (dapagliflozin, empagliflozin) and a SGLT1/2i (sotagliflozin) on various biological parameters (glucosuria, glycemia, glucagonemia, insulinemia) in mice. mRNA expression of SGLT2 and other glucose transporters was assessed in rat, mouse, and human FACS-purified α- and β-cells, and by analysis of two human islet cell transcriptomic datasets. Immunodetection of SGLT2 in pancreatic tissues was performed with a validated antibody. The effects of dapagliflozin, empagliflozin, and sotagliflozin on glucagon and insulin secretion were assessed using isolated rat, mouse and human islets and the in situ perfused mouse pancreas. Finally, we tested the long-term effect of SGLT2i on glucagon gene expression.

Results

SGLT2 inhibition in mice increased the plasma glucagon/insulin ratio in the fasted state, an effect correlated with a decline in glycemia. Gene expression analyses and immunodetections showed no SGLT2 mRNA or protein expression in rodent and human islet cells, but moderate SGLT1 mRNA expression in human α-cells. However, functional experiments on rat, mouse, and human (29 donors) islets and the in situ perfused mouse pancreas did not identify any direct effect of dapagliflozin, empagliflozin or sotagliflozin on glucagon and insulin secretion. SGLT2i did not affect glucagon gene expression in rat and human islets.

Conclusions

The data indicate that the SGLT2i-induced increase of the plasma glucagon/insulin ratio in vivo does not result from a direct action of the gliflozins on islet cells.

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Gliflozins (SGLT2 and SGLT1/2 inhibitors) increase plasma glucagon/insulin ratio.

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SGLT2 is not expressed in rodent and human pancreatic α- and β-cells.

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SGLT1 is however expressed in human α-cells.

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SGLT2 and SGLT1/2 inhibitors do not directly affect glucagon and insulin secretion.

Rationale for Timely Insulin Therapy in Type 2 Diabetes Within the Framework of Individualised Treatment: 2020 Update

Type 2 diabetes is characterised by chronic hyperglycaemia and variable degrees of insulin deficiency and resistance. Hyperglycaemia and elevated fatty acids exert harmful effects on β-cell function, regeneration and apoptosis (gluco-lipotoxicity). Furthermore, chronic hyperglycaemia triggers a vicious cycle of insulin resistance, low-grade inflammation and a cascade of pro-atherogenic processes. Thus, timely near to normal glucose control is of utmost importance in the management of type 2 diabetes and prevention of micro- and macroangiopathy. The majority of patients are multimorbid and obese, with critical comorbidities such as cardiovascular disease, heart failure and chronic kidney disease. Recently published guidelines therefore recommend patient-centred risk/benefit-balanced use of oral glucose-lowering drugs or a glucagon-like peptide 1 (GLP-1) receptor agonist, or switching to insulin with glycated haemoglobin (HbA1c) out of target. This article covers the indications of early insulin treatment to prevent diabetes-related complications, particularly in subgroups with severe insulin deficit, and to achieve recovery of residual β-cell function. Furthermore, the individualised, risk/benefit-balanced, timely initiation of insulin as second and third option is analysed. Timely insulin initiation may prevent diabetes progression, reduce diabetes-related complications and has less serious adverse effects. Basal insulin is the preferred option in most clinical situations with consequences of undertreatment of chronic hyperglycaemia.

BMP9 Reduces Bone Loss in Ovariectomized Mice by Dual Regulation of Bone Remodeling

Bone remodeling is dynamic and is tightly regulated through bone resorption dominated by osteoclasts and bone formation dominated by osteoblasts. Imbalances in this process can cause various pathological conditions, such as osteoporosis. Bone morphogenetic protein 9 (BMP9), a biomolecule produced and secreted by the liver, has many pharmacological effects, including anti-liver fibrosis, antitumor, anti-heart failure, and antidiabetic activities. However, the effects of BMP9 on the regulation of osteoblast and osteoclast functions and the underlying molecular mechanism(s) have not yet been investigated. In this study, BMP9 increased the expression of osteoblastogenic gene markers, such as ALP, Cola1, OCN, RUNX2, and OSX, and ALP activity in MC3T3-E1 cells by upregulating LGR6 and activating the Wnt/β-catenin pathway. BMP9 also suppressed receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast differentiation of bone marrow macrophages (BMMs) by inhibiting the Akt-NF-κB-NFATc1 pathway. More importantly, in an ovariectomy (OVX) mouse model, BMP9 attenuated bone loss and improved bone biomechanical properties in vivo by increasing bone-forming activity and suppressing bone resorption activity. Accordingly, our current work highlights the dual regulatory effects that BMP9 exerts on bone remodeling by promoting bone anabolic activity and inhibiting osteoclast differentiation in OVX mice. © 2020 American Society for Bone and Mineral Research.

Early Treatment with Empagliflozin and GABA Improves β-Cell Mass and Glucose Tolerance in Streptozotocin-Treated Mice

While the autoimmune character of T1D (type 1 diabetes) is being challenged, it is currently recognized that inflammation plays a key role in its development. We hypothesized that glucotoxicity could contribute to β-cell mass destruction through participation in islet inflammation. We evaluated the potential of empagliflozin (EMPA) and GABA (gamma-aminobutyric acid) to protect β-cell mass against glucotoxicity and to increase β-cell mass after diagnosis of T1D. Empagliflozin is a SGLT2 (sodium-dependent glucose cotransporter) inhibitor which thereby blocks glucose recapture by the kidney and promotes glucose excretion in urine. GABA is an inhibitory neurotransmitter, which stimulates α-to-β cell transdifferentiation. In streptozotocin-treated mice, empagliflozin and/or GABA were delivered for a period of five days or three weeks. As compared to untreated T1D mice, EMPA-treated T1D mice had decreased FFA (free fatty acid) levels and improved glucose homeostasis. EMPA-treated T1D mice had higher islet density, with preserved architecture, compared to T1D mice, and EMPA-treated T1D mice also differed from T1D mice by the total absence of immune cell infiltration within islets. Islets from EMPA-treated mice were also less subjected to ER (endoplasmic reticulum) stress and inflammation, as shown by qPCR analysis. Glucose homeostasis parameters and islet area/pancreas area ratio improved, as compared to diabetic controls, when T1D mice were treated for three weeks with GABA and EMPA. T1D EMPA+GABA mice had higher glucagon levels than T1D mice, without modifications of glucagon area/islet area ratios. In conclusion, empagliflozin and GABA, used in monotherapy in streptozotocin-induced diabetic mice, have positive effects on β-cell mass preservation or proliferation through an indirect effect on islet cell inflammation and ER stress. Further research is mandatory to evaluate whether empagliflozin and GABA may be a potential therapeutic target for the protection of β-cell mass after new-onset T1D.

Mechanisms of β-cell dedifferentiation in diabetes: recent findings and future research directions

Like all the cells of an organism, pancreatic β-cells originate from embryonic stem cells through a complex cellular process termed differentiation. Differentiation involves the coordinated and tightly controlled activation/repression of specific effectors and gene clusters in a time-dependent fashion thereby giving rise to particular morphological and functional cellular features. Interestingly, cellular differentiation is not a unidirectional process. Indeed, growing evidence suggests that under certain conditions, mature β-cells can lose, to various degrees, their differentiated phenotype and cellular identity and regress to a less differentiated or a precursor-like state. This concept is termed dedifferentiation and has been proposed, besides cell death, as a contributing factor to the loss of functional β-cell mass in diabetes. β-cell dedifferentiation involves: (1) the downregulation of β-cell-enriched genes, including key transcription factors, insulin, glucose metabolism genes, protein processing and secretory pathway genes; (2) the concomitant upregulation of genes suppressed or expressed at very low levels in normal β-cells, the β-cell forbidden genes; and (3) the likely upregulation of progenitor cell genes. These alterations lead to phenotypic reconfiguration of β-cells and ultimately defective insulin secretion. While the major role of glucotoxicity in β-cell dedifferentiation is well established, the precise mechanisms involved are still under investigation. This review highlights the identified molecular mechanisms implicated in β-cell dedifferentiation including oxidative stress, endoplasmic reticulum (ER) stress, inflammation and hypoxia. It discusses the role of Foxo1, Myc and inhibitor of differentiation proteins and underscores the emerging role of non-coding RNAs. Finally, it proposes a novel hypothesis of β-cell dedifferentiation as a potential adaptive mechanism to escape cell death under stress conditions.

Empagliflozin Prevents Worsening of Cardiac Function in an Experimental Model of Pressure Overload-Induced Heart Failure

This study sought to determine whether the sodium/glucose cotransporter 2 (SGLT2) inhibitor empagliflozin improved heart failure (HF) outcomes in nondiabetic mice. The EMPA-REG OUTCOME (Empagliflozin, Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients) trial demonstrated that empagliflozin markedly prevented HF and cardiovascular death in subjects with diabetes. However, despite ongoing clinical trials in HF patients without type 2 diabetes, there are no objective and translational data to support an effect of SGLT2 inhibitors on cardiac structure and function, particularly in the absence of diabetes and in the setting of established HF. Male C57Bl/6 mice were subjected to either sham or transverse aortic constriction surgery to induce HF. Following surgery, mice that progressed to HF received either vehicle or empagliflozin for 2 weeks. Cardiac function was then assessed in vivo using echocardiography and ex vivo using isolated working hearts. Although vehicle-treated HF mice experienced a progressive worsening of cardiac function over the 2-week treatment period, this decline was blunted in empagliflozin-treated HF mice. Treatment allocation to empagliflozin resulted in an improvement in cardiac systolic function, with no significant changes in cardiac remodeling or diastolic dysfunction. Moreover, isolated hearts from HF mice treated with empagliflozin displayed significantly improved ex vivo cardiac function compared to those in vehicle-treated controls. Empagliflozin treatment of nondiabetic mice with established HF blunts the decline in cardiac function both in vivo and ex vivo, independent of diabetes. These data provide important basic and translational clues to support the evaluation of SGLT2 inhibitors as a treatment strategy in a broad range of patients with established HF.